i cant play m4a file(supposedly mpeg-4).i have no problem playing mp3 ,wav etc. MS WMP was supposed to in WMP 12.
Is this a file from Apple iTunes?
Have you already tried to play another m4a file? As the file may be damaged, or it’s something not compatible inside the m4a container.
Can you play the file with Movies & TV app?
Download and install K-Lite Codec pack. Reboot.